The highest cyclic rate gas operated single barrel weapons firing conventional cartridges utilize a primary mass (called an actuator or bolt carrier) which are directly, or indirectly, driven by gas tapped from the barrel. The kinetic energy of the primary mass (derived from the gas from the barrel) serves to unlock the bolt (secondary mass) and to carry the combined primary/secondary mass rearward to operate the weapon.
It is well known that when the primary mass contacts, unlocks and picks up the secondary mass, that there is a significant drop in velocity of the combined primary/secondary mass as compared to the velocity of the primary mass before impact with the secondary mass.
It is also well known that the upper limit of cyclic rate is governed by, among other things, the highest velocity at which a spring can be compressed without damaging the spring.
This means that the cyclic rate of a gas operated weapon is limited by the velocity of the operating parts, which is in turn, governed by the loading velocity of the spring. Since the initial velocity of the primary mass is limited by the loading velocity which the spring can tolerate, it follows that the velocity of the combined primary/secondary mass will be somewhat below the maximum loading velocity which the spring can tolerate, resulting in a slower cycle time than if the operating parts could continue at the initial velocity of the primary mass.
A number of attempts have been made to develop low velocity grenade launchers employing gas powering systems. These have not been successful because conventional gas systems have been employed. Conventional gas systems are well suited for weapons employing typical (say 50,000 psi) cartridges but such systems only extract a very small percentage of the gas generated in firing. In conventional systems, a small percentage of the gas is adequate because the gas is at very high pressure and contains a relatively great amount of energy. In contrast to typical cartridges, the pressure in a grenade launcher barrel just ahead of the chamber may be less than 5,000 psi. In addition to the very low initial pressure, what little pressure there is, decrease very quickly due to the low quantity of powder consumed and the very high expansion ratios associated with grenade launcher systems. This means that in order for a gas system to operate properly under such conditions, a relatively large percentage of gas generated must be quickly trapped, and then the energy in the trapped gas must be efficiently extracted. The subject invention accomplishes these ends.